[test] Mute failing irText tests

compiler/testData/ir/irText/stubs/builtinMap.kt

@@ -1,5 +1,6 @@
 // WITH_STDLIB
 // FULL_JDK
+// TARGET_BACKEND: JVM_IR
 
 fun <K1, V1> Map<out K1, V1>.plus(pair: Pair<K1, V1>): Map<K1, V1> =
         if (this.isEmpty()) mapOf(pair) else LinkedHashMap(this).apply { put(pair.first, pair.second) }

compiler/testData/ir/irText/stubs/constFromBuiltins.kt

@@ -1,3 +1,5 @@
 // DUMP_EXTERNAL_CLASS: kotlin/Int
+// IGNORE_BACKEND_K2: JS_IR
+// IGNORE_BACKEND_K2: JS_IR_ES6
 
 val test = Int.MIN_VALUE